Efforts to improve the finish and corrosion resistance of various products such as automobiles have resulted in the use of dip and spray tanks to precoat metallic articles with caustic solutions, phosphate solutions, and other chemical solutions prior to painting. It is necessary in the typical case to enclose these tanks to contain spray and/or to control evaporation and escape of vapors into the adjacent areas of the plant. Structural steel enclosures have been used for this purpose but have generally been unsatisfactory because of the tendency of the spray and vapors from the bath to attack the metal structural components of the enclosure. Even where non-corroding materials such as stainless steel have been used, the beams and other structural components of the enclosures are still exposed to the vapors and spray and eventually produce rust and maintenance problems. In addition, stainless steel is an expensive structural material.
Corrosion produces a number of problems including (1) the deterioration and unsightliness of the enclosure; (2) contamination of the bath or spray by corrosion containing condensate; and, (3) spoilage of the workpieces due to corrosion and corrosive materials falling thereon during the finishing operation.
It is theoretically possible to construct the entire enclosure from stainless steel but this is generally regarded as prohibitively expensive.